An evaporation control system of a vehicle is generally equipped with an activated carbon canister on a fuel tank vapor line. When the engine is running, the evaporation control system returns the fuel vapors collected in the canister to the intake portion of the engine, through a purge line and a purge control valve, under the control of an Electronic Control Unit (ECU).
However, if the fuel tank is overfilled, the fuel level may be up to the canister or the purge line. Provided that the purge control valve is opened after the engine ignition key is turned on, the liquid fuel remaining in the purge line flows into the intake portion of the surge tank, causing a loss of engine power due to an extremely low air-fuel ratio (A/F).
Therefore it would be desirable to detect the presence of liquid fuel in the purge line before engine power is lost, and to control operation of the purge control valve based on whether or not liquid fuel exists in the purge line.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art that is already known in this country to a person of ordinary skill in the art.